DragonFly On-Line Manual Pages

VGA_SWITCHEROO(4)     DragonFly Kernel Interfaces Manual     VGA_SWITCHEROO(4)

NAME
     vga_switcheroo, apple_gmux -- support for Apple laptops with dual GPUs

SYNOPSIS
     To enable support of dual GPUs in kernel, include the following line in
     the kernel configuration file:

           options VGA_SWITCHEROO

     When the system has booted, load the apple_gmux driver before the native
     graphics drivers, for example i915(4).

     Alternatively, you can put these two lines in rc.conf(5):

           apple_gmux_load="YES"
           i915_load="YES"

     As a result, vga_switcheroo switches the gmux controller so that all
     output comes from the IGD.

DESCRIPTION
     Apple MacBook Pro laptops have hybrid graphics, i.e. two GPUs, one being
     the integrated graphics device (IGD) and the other being the discrete
     graphics device (DIS), sometimes called the dedicated graphics device.
     Gmux is a microcontroller that controls the output of these GPUs.

     vga_switcheroo is the higher level module that facilitates switching
     between the two GPUs using the lower level apple_gmux driver.  When the
     system boots and vga_switcheroo is enabled, apple_gmux registers with it.
     It then acts as a handler.  The two graphics adapters will also detect
     the presence of vga_switcheroo and register as clients.

IMPLEMENTATION NOTES
     In the current DragonFly specific implementation, upon detecting the
     presence of apple_gmux, the Intel driver will call vga_switcheroo to
     switch the gmux so that all output comes from the IGD.  Switching to DIS
     is not yet supported.

HARDWARE
     Apple MacBook Pro laptops with dual GPUs.

SEE ALSO
     i915(4), rc.conf(5)

     https://01.org/linuxgraphics/gfx-docs/drm/gpu/vga-switcheroo.html

HISTORY
     The vga_switcheroo driver was added in DragonFly 4.9.

AUTHORS
     The vga_switcheroo driver was ported to DragonFly from linux 4.8 by
     Peeter Must.  He also wrote this manual page.

DragonFly 4.7                    May 30, 2017                    DragonFly 4.7